1. Field of the Invention
The disclosure is related to a pillar for a motor vehicle, and mores specifically, to a center pillar for a passenger car.
2. Description of the Related Art
Vehicle pillars are part of the vehicle bodywork and connect the vehicle roof, in particular the roof frame, to the vehicle floor, usually in the form of a sill. Vehicle pillars are as a rule manufactured from sheet-metal material with a monocoque construction and serve, as a structural component of the vehicle bodywork, for protecting the vehicle occupants, but also make a substantial contribution to the overall stiffness of the motor vehicle. In particular the center pillar serves to provide side impact protection and prevents another party in an accident or an object from penetrating too far into the passenger compartment of the vehicle. In addition, the side doors are fixed in position at the center pillar by hinges or locks.
In the last 20 years, more and more pillars composed of a steel alloy have been manufactured by form-hardening with extremely high strength properties, as a result of which it has been possible to reduce the wall thickness significantly compared to high-strength cold-formed steels and therefore to save weight. In this context, a non-shaped sheet-metal material composed of a hardenable steel alloy or a pre-shaped sheet-metal material is heated to above the austenitizing temperature of the steel alloy and re-shaped and form-hardened in a cooled press forming tool to form the motor vehicle component.
EP 1 180 470 A1 discloses a form-hardened pillar in the form of a center pillar, also referred to as B pillar. The latter has an upper longitudinal section with an upper coupling section for attachment to a roof frame, and a central longitudinal section which is embodied in the form of a hat profile in cross section. A lower coupling section for attachment to a sill has a lower tensile strength as a predefined deformation point, which is achieved by heating, reduced in the lower coupling section, to less than the austenitizing temperature. In this way, sufficiently defined deformation behavior for protecting the vehicle occupant on the side of the side impact event is to be ensured. In particular, deformation in the region of the upper body of the vehicle occupant is to be prevented in this way by bending or folding in the center of the pillar. A disadvantage with the known component design is that a specific heating process has to be carried out before the form-hardening or alternatively after the form-hardening in order to ensure targeted deformation, and in addition, owing to the relatively soft predefined deformation region, the wall thickness can be reduced only to a limited degree, which holds potential for further lightweight design optimization.
DE 100 49 660 B4 discloses a form-hardened shell part for a hollow carrier of a vehicle bodywork. The shell part is composed of a basic piece of sheet metal and of a relatively small, locally arranged reinforcement piece of sheet metal connected thereto, and is heated for the purpose of austenitization. Subsequently, common re-shaping and form-hardening are carried out in a cooled press forming tool. In this way, allowance is to be made better for the lightweight design, but further improvements are to be aimed at with respect to the corrosion behavior between the pieces of sheet metal and with regard to the deformation behavior.